Cmd costructor. Useful when you want to artificially emit Cmd from update function.

performed : Cmd String
performed =
    perform "foo"

"real world" example:

type alias Model =
    ()


type Msg
    = Fire
    | FireRockets


update : Msg -> Model -> ( Model, Cmd Msg )
update msg () =
    case msg of
        Fire ->
            ( (), perform FireRockets )


        FireRockets ->
            Debug.crash "World ended:("

Similar to perform but takes Result msg and performs action only on Ok.

attempted : Cmd String
attempted =
  attempt <| Ok "I'm fine"


attempt (Err "Failed") == Cmd.none
--> True

Similar to attempt but works with Maybe instead

maybeCmd : Cmd Int
maybeCmd =
    maybe <| Just 1


maybe Nothing == Cmd.none
--> True

Construct from Result.

resultCmd : Cmd (Result Never Int)
resultCmd =
  fromResult identity (Ok 1)


fromResult identity (Err ())
--> Cmd.none

Construct from Maybe.

maybeCmd : Cmd (Maybe Int)
maybeCmd =
  identity (Just 1)


fromMaybe identity Nothing
--> Cmd.none

Creates pair model with Cmd.none

pair : ( String, Cmd msg )
pair = pure "foo"


pair
  |> Tuple.second
  |> ((==) Cmd.none)
--> True

Add Cmd to model to create a pair.

Add new cmd to an existing pair.

Trigger Cmd from Msg and create a pair

Add new trigger of Msg to an existing pair.

Add new cmd to an existing pair under a certain condition.

prevCmd : Cmd String
prevCmd =
    perform "foo"


newCmd : Cmd String
newCmd =
    perform "bar"


( "model", prevCmd )
  |> addIf False newCmd
  |> Tuple.second
  |> ((==) prevCmd)
--> True